In the past, vehicle drive shafts have been formed of a steel tube having a high flexural modulus with forged steel yokes welded to each end of the steel tube. With both the tube and yokes formed of steel, the drive shaft is a relatively heavy structure. To maintain an acceptably high critical speed with a long tubular steel drive shaft, the drive shaft is often formed of short multiple sections and shaft support bearings are positioned along the length of the drive shaft which act to rotationally support the shaft sections.
Recently there has been considerable activity in the development of composite drive shafts which are composed of a fiber reinforced resin tubular member or shaft and lightweight metal, such as aluminum, yokes. A composite drive shaft achieves a substantial weight reduction as compared to a steel drive shaft and due to the lighter weight, a one-piece composite shaft can replace the multi-sectioned steel shafts, with the resultant elimination of the shaft support bearings which are utilized with a multi-sectioned steel shaft.
A problem in the fabrication of a composite drive shaft has been the lack of an adequate connection between the fiber reinforced resin tube and the yokes. In one approach to providing an adequate connection between the tube and the yokes, the ends of the tube, which surround the sleeve portion of the yoke, are connected to the sleeve portion by rivets. In another approach, as shown in U.S. Pat. No., 4,279,275, the sleeve portion of the yoke is provided with a plurality of longitudinally extending grooves and the resin impregnated fibrous material is wound over the grooves to provide an improved mechanical connection between the tube and the yokes.
In U.S. Pat. No. 4,358,284, the sleeve portion of the yoke is formed with circumferentially extending grooves or threads and the fibrous material is wound in the grooves to provide an improved attachment, while in U.S. Pat. No. 4,380,443, a series of angularly extending pins are employed to interconnect the wound tube with the sleeve portion of the yoke.
U.S. Pat. No. 4,248,062 proposes to increase the bond between the wound tube and the sleeve portion of the yoke by employing a specific winding pattern including longitudinal helical and circumferential windings.